Aluminum a/c lines instead of barrier hose

blk911 · 08-22-2007, 03:34 PM

First of all, I am no engineer, but I am just about convinced I need to return my upgraded A/C system to R12. Already got a Sanden, Procooler, Hi-efficiency serpentine evaporator and expansion valve and barrier hoses. 134A just not cutting it in Texas heat.I don't mind spending $250 or so for the intial charge, but don't want to do it every year and therefore am considering replacing all my barrier hoses with custom fabricated aluminum or steel lines. Might shave a few pounds too.

Any suggestions as to size? I can get .375" o.d. with .056 wall in 6061 aluminum or would steel be more preferable? any recommendations would be appreciated.

Por_sha911 · Por_sha911's Garage

I can't answer your question about AL lines but if you have leakage it shouldn't be from the barrier hose. Have you checked for leaks in other places (O-rings, front condensor)? As far as 134A vs 12 I have been told 12 is better but with all that you've listed you should have decent cooling. What temperature do you call "not cutting it Texas heat"? Are you sure that system is not over or undercharged?

blk911 · 08-22-2007, 03:53 PM

Joe,

Reputable shop pulled vaccum on the system and it held for at least an hour with no leakdown. Had them charge the system and got 32 degrees at the vent with ambient of about 85, but pressures were pretty high, can't remember the numbers exactly, but seemed like they were around 245 on the high side. I have been told 134 can't dissipate that much heat like R12.

Por_sha911 · Por_sha911's Garage

I've been told the same on the 134. 245 is too high. My question is why do you think you will have to spend $250 every year? If your system is solid, you shouldn't have to replace coolant every year. Am I missing something?

jbrinkley · 08-22-2007, 04:15 PM

a couple more dollars can get you a toyota truck and have the best AC around, I say truck because of the air volume aspect.

I understand though about wanting AC in a 911. It just doesn't make sense though.

maybe everywhere other than the southern africa hot united states.

blk911 · 08-22-2007, 06:57 PM

I have a Toyota truck thank you and yes, it has great AC. But sometimes, I would like to drive my 911 to work without sweating and in Austin, Texas, during about five maybe six months a year, it is no fun. What is it with all you who think having an AC in a fine automobile like a Porsche is sacriligeous?

khamul02 · khamul02's Garage

Spend some of that 250 a year and add more condensers. One in the front wheel well with a fan and then possibly one in the rear well as well.

jbrinkley · 08-22-2007, 07:23 PM

I don't think it's sacrilegous at all, I applaud the effort. Some people go to great lengths to get $ome cold air. It just doesn't make sense to me that's all

Jim Sims · 08-22-2007, 08:14 PM

Doc's Blocks (see link below) sells aluminum and steel refrigerant tubing for automotive use and braze on hose crimp fittings to incorporate rubber hose sections/ends as required. They also sell easy to use braze alloy "rings" (complete with a flux core) for the tubing joints and a "how to braze aluminum tubing" instructional DVD; one brazes aluminum with a common propane torch. For typical 911 service, I doubt the extra strength/fatigue life of the steel tubing would be useful. 3/8" aluminum tubing matches #6 hose, 1/2" matches #8 hose and 5/8" matches #10 hose. There is a heat transfer disadvantage in using metal tubing in place of the #10 rubber suction hose (runs between the evaporator and compressor or in the case of your car between the Procooler and the compressor) as this line may be colder than the environment and will pick up heat (metal conducts heat much better than rubber) that the condensors must then discharge. If you elect to make the suction line metal I suggest you apply some type of thermal insulation to it.

On two 911's I have replaced the portion of the #6 high pressure refrigerant line that runs forward under the rocker with 3/8" alumimum 3003-0 ASTM-B 483tubing from Doc's Blocks; the tubing weighs less than the hose plus the air moving over the tubing provides some additional condensing action.

http://docsblocks.com/

Cheers, Jim

tcar · 08-23-2007, 03:42 AM

Also, can't find it now, but there is finned aluminum tubing that does act as a condenser. Do a search, I saw it on Pelican.

khamul02 · khamul02's Garage

tcar,
Isn't that for the oil lines? That would be very cool

if there were a finned line you could replace the high pressure side lines with. That would be a good deal of condenser that gets added to the system. Great concept.

Barrpete · 08-23-2007, 05:49 AM

You might actually be a bit overcharged, which can reduce the efficiency of your system. This is the chart I got from Rennaire for 134a:

High Side:
115 to 200 psi for 70 to 80 deg F ambient temp*
140 to 235 psi for 80 to 90 deg F ambient temp*
165 to 270 psi for 90 to 100 deg F ambient temp*
210 to 310 psi for 100 to 110 deg F ambient temp*

Also, do you have the condensor in the front? And is the fan working?

Quote:

Originally Posted by blk911

Reputable shop pulled vaccum on the system and it held for at least an hour with no leakdown. Had them charge the system and got 32 degrees at the vent with ambient of about 85, but pressures were pretty high, can't remember the numbers exactly, but seemed like they were around 245 on the high side. I have been told 134 can't dissipate that much heat like R12.

skipdup · 08-23-2007, 06:10 AM

blk911- I run an underbelly condenser on my 930. Mine will absolutely freeze you out of the car if you leave it on high or medium - in San Antonio, during summer, in stop-and-go traffic. My wife literally has to wear a sweater.

I run R12, but I also run the tiny rear condenser due to the intercooler.

If you ever make it down this way you should check it out. I think you might be surprised.

- Skip

tcar · 08-23-2007, 10:05 AM

I was also going to say, I have R12, front and rear stock condensers and lines, York compressor, on my targa and I cannot run it on high for very long even when it's over 100.

I do have to have the freon 'topped up' every 2-3 years, tho.

blk911 · 08-24-2007, 01:34 PM

Jim Sims, as usual, your comments and expertise is much appreciated, thank you very much.

Skipdup, I got a line on an underbelly condensor for about $400 and seriously considering it as well as a stronger evaporator blower motor and bulkhead mods to improve air movement. Did you have any other system upgrades on your car?

Barrpete, thank you for the pressure chart, I'll check it out.

My SC is triple black and so I need all the help I can get before I have a meltdown and paint it white or silver.

tcar · 08-25-2007, 07:58 PM

Many silvers are as hot as black...

kuehl · kuehl's Garage

How many ounces of R134a were put in the system?

mthomas58 · 05:48 AM

Quote:

Originally Posted by skipdup

Mine will absolutely freeze you out of the car if you leave it on high or medium - in San Antonio, during summer, in stop-and-go traffic. My wife literally has to wear a sweater.

- Skip

So, dreams really do come true!

I hope to be able to say the same thing next year after some winter mods to replace my remaining 20 year old parts and add an underbelly condenser & Procooler.

JeremyD · JeremyD's Garage

Quote:

Originally Posted by blk911

Jim Sims, as usual, your comments and expertise is much appreciated, thank you very much.

Skipdup, I got a line on an underbelly condensor for about $400 and seriously considering it as well as a stronger evaporator blower motor and bulkhead mods to improve air movement. Did you have any other system upgrades on your car?

Barrpete, thank you for the pressure chart, I'll check it out.

My SC is triple black and so I need all the help I can get before I have a meltdown and paint it white or silver.

care to share your line on the $400 underbelly condensor?

Scott98 · Scott98's Garage

Quote:

Originally Posted by skipdup

blk911- I run an underbelly condenser on my 930. Mine will absolutely freeze you out of the car if you leave it on high or medium - in San Antonio, during summer, in stop-and-go traffic. My wife literally has to wear a sweater.

I run R12, but I also run the tiny rear condenser due to the intercooler.

If you ever make it down this way you should check it out. I think you might be surprised.

- Skip

How is that possible? When I bought my '87 911, the A/C had no freon. I bought a new R/D, added oil, drained oil out of the compressor and added new oil, pulled a vacuum and added Freeze-12. My A/C sucks. I have both front and rear condensors too. Don't say its the refrigerant because I've used Freeze-12 with great success in other cars and know many people who have too. I thought 911 A/C just sucked unless you did some upgrades. Am I missing something???

Scott